This may be obvious, but does this rule out Canon as a brand as they do not have such a lens and there is no hint of them launching such a lens?

If a lens such as the 10.5 Nikkor or the 8mm Olympus is a must have item should I not bother to look at Canon cameras unless I like the look of the 5D?

That's the biggest reason I'll probably upgrade to the 5D. I agree that Canon is unlikely to come out with an EF-S 180 degree fisheye. I suspect Sigma will come out with one soon. They have execellent 15mm and 8mm FE lenses.

No doubt that Nikon have a big advance in the super WA area, you can do 180 degrees shots with a relative not so expensive camera like the D70.
If this type of photography is what interest you and you don't want or can't buy the much more expensive FF option then Nikon is the way for you.

I've been using the Inon AD 165 lens on my Canon A95 compact and finding it very useful indeed, especially in murky UK waters. Admittedly its not 180 degrees but I suppose at around 165 degrees it's getting there.

It's this experience that makes me lust after a similar angle of coverage on an SLR. I think I'd find only a 15mm on a Canon 20D or a 350D a bit dissapointing. A full frame Canon 5D seems a real comitment if I'm still paralyzed by indecision on camera/housing choices.

A 180 degree fisheye (FE) is my most-used lens for murky water wide angle. Conditions in Alaska are no better than UK waters. A FE is a must have if you are going to 'upgrade' to a dSLR. FE's are quite useful in clearish waters too!
Tom

Oh I totally agree with you guys - once you've been diving for a while, a FF Fisheye is a must. I loved using mine in Bali when viz was low.

But it's definitely a "specialty" lens, and not as versatile as a wideangle zoom like a Sigma 10-20. I have a 1.25 crop camera, and when I bought it I wasn't particularly worried about whether or not I'd be able to shoot 180 degree fisheye. I still like the fisheye on the 1.3x crop camera, it's very wide, and probably easier to shoot for a beginner like me since I don't photograph my fins as much. :-)

Gerard, that's true for rectilinear wide angle lenses. The fisheyes (either Canon or Nikon) have a distorted angle of coverage of 180 degrees, regardless if they are 16, 15 or 10.5mm. The 10-22 is a rectilinear wide angle, with a coverage much smaller than the fisheyes. Different lens designs for different applications.

I am a big fisheye user. And could not imagine UW shooting without it. I use it for about 90% of my wide angle photography and 100% of my (limited) photography in the UK.

I agree with James that fisheyes are not idea for beginners. But once you have learned to use them then nothing else will do! And certainly Trevor is not beginner at wide angle.

Now that the Canon 5D is available (although not yet housable) you don't really have to differentiate the brands on fisheyes (as previously the 1Ds, as a new camera, was out of nearly everyones price range). But the 5D is very expensive £2300 in the UK. So if you are looking in the sub £1000 range for a body then Nikon mount bodies do still offer an advantage.

I would also look towards what camera and housing brands your regular buddies have. Choosing the same as them is a good way to ensure backups and different lenses are available when you travel.

On the note of fisheyes being of limited use - I rarely ever use one although most of my underwater photography is in Britain and Ireland, although I do have a Canon 15mm fisheye lens. It depends on how and what you shoot and which lenses suit your style and subjects.

If you like the smaller (not full frame) format then Nikon are a logical choice, especially as the Canon FF cameras are more expensive. However things may change. FF cameras will probably get cheaper and, who knows, Canon may produce a fisheye for their smaller format cameras.

If you really want a fisheye lens now, then look closely at Nikon at the moment, if you are happy to key into their smaller format.

Actually, this is probably a good example for the 10.5's usefulness in low light.

My first dive on this plane, the water was much clearer and the vis was pretty good. Later in the week, on our second dive, vis has dropped substantially. Although the 10.5 really pushes the image away, I was quite near the wreck, perhaps just a few feet from the prop.

The ability to get closer kept the major part of the subject from being swallowed up by the fog that's beginning to envelope the tail. It would have been interesting to see how much further back the 15mm would have pushed me to get the same framing v.s. the 10.5. (Full frame btw)

And I'm very much looking forward to using this lens in La Paz where I hope to find a spot for Alex's magic filter as well. Perhaps with the Sealions.